Spark gap mechanism



3 Sheets-Sheet l INVENTOR.

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Aug. 22, 1950 G. P. GOODE ET AL `SPARK GAP MECHANISM Filed Oct. 28, 1948 Aug. 22, 1950 G. P. GooDE ET Ax.

SPARK GAP MECHANISM Filed oct. 28, 1948 5 Sheets-Sheet 2 wg w .am e y m ZZ 6 m 1A| f1 e QU .0... 6....; f 1 ZM 4%? fa 7DIIENTOR.

Mja/117mg A TTRNEYS,

atentec ug. 22, 195() SPARK GAP MECHANISM Godfrey P. Goode, Covington, Ky., and iCarl K. Gieringer, Cincinnati, Ohio, assignors to The Liebel-Flarsheim Company,

corporation of Ohio Cincinnati, Ohio, a

Application October 28, 1948, `Serial No. 57,026

(Cl. Z50- 38) 22 Claims. 1

This invention relates to spark gap mechanisms of the type adapted for operation in conjunction with charged condenser circuits for producing high frequency electrical energy. Such apparatus is employed in radio transmission and for other purposes, but the invention is particularly useful in high frequency spari: gap machines for surgical and therapeutic purposes and, therefore, is disclosed essentially in that environment.

A spark gap mechanism consists of one or more pairs of spaced electrodes which are charged electrically for the emanation of sparks between them. These sparks are intensely hot and, although metals of heat-resistant or refractory nature have been utilized in fabrication of the electrodes, still, even such materials are pitted and become Worn away during usage of the apparatus. The spacing of the electrodes, that is,

the width of the spark gap determines the .voltage of the electrical energy which is provided from the mechanism. In general, the spark at a wide gap is hotter than at a narrow gap, and therefore exerts a greater deteriorating effect upon the electrodes between which it is produced.

Various devices are available which respond to the heat of the sparks to compensate for expansion and thereby maintain uniformity of gap width throughout a given period of operation of the apparatus. However, these devices are incapable of providing adequate compensation for the wearing away of the electrodes and, in surgical and therapeutic spark gap oscillators, it is highly desirable that gap width uniformly may be maintained, or readily obtained, in the day to day use of the equipment, since the characteristics of the discharge current from the apparatus otherwise will change.

This invention contemplates a spark gap mechanism capable of providing uniform gap spacing throughout the life of the electrodes or the apparatus. Otherwise expressed, a primary objective has been to provide an apparatus in which the electrodes conveniently may be set, or reset from time to time, to assume predetermined gap width positions. Such adjustments may be made conveniently vas an incident to placing the apparatus into electrical operation.

A suitable spark discharge may be obtained by the use of a single pair of electrodes, spaced a substantial distance apart from one another. Such an apparatus commonly is called a single gap device. However, more satisfactory results are usually obtained if the machine comprises a Cil series of gaps constituted by a plurality of pairs of electrodes connected electrically in series. In such cases, the gap widths are smaller, and, since the sparks are shorter, the electrodes suer less deterioration. In mechanism of this type, it is highly desirable that all of the gaps be of uniform width; otherwise, that pair of electrodes which is most widely spaced will produce a different discharge voltage than a pair which is spaced closely, and will suffer more surface pitting to aggravate the condition as time goes on.

In recognition of these inequalities, which generally exist in apparatus now available, it is an objective of the present invention to provide a mechanism for uniformly spacing all of the respective electrodes in a series of pairs, one from another, such that spark gaps of equal width, which they then delineate, will produce discharge currents of uniform characteristics. Also, even though one or a series of spark gaps initially may be of the desired width and uniformity of width, still, during a period of electrical operation of the equipment, some electrodes will inherently beworn, pitted, or deteriorated more than others, and even though a machine initially conforms to optimum conditions, these conditions will vary from optimum during periods of usage. Therefore, it is an objective of the invention to provide a simple apparatus for resetting the gap widths such that optimum conditions of gap width may be restored or re-established periodically.

Other objectives and features of the invention are described at later points in this specication in relation to characteristic conditions normally encountered in the operation of the apparatus, and, therefore, are not described in detail at this point.

Briefly, this invention is predicated upon the concept of establishing a predetermined spark gap space between a pair of electrodes by moving one or the other or both electrodes of the pair through a predetermined distance, from a position of engagement thereof. Otherwise eX- pressed, engagement of the electrodes is utilized as a standard or reference point from which gap width is measured, or from which the separating movement is initiated, since this standard remains constant no matter how the electrodes may have been worn While they were spaced apart during any preceding period of operation.

Having the electrodes in engagement, they are separated a predetermined distance by the movement of a shifter which is adapted to be actuated through a predetermined fixed distance.

tively vvith the shifter after the electrodes havev been brought into engagement, such that movement of the shifter thereafter Will provide the desired gap width. Such couplings herein are termed wear compensators; they assumecouplingY positions between the shifter and the meansby which the electrodes are spaced, depending on the. wear condition of. thev electrodes and thus discriminate, by lthe positions they assume, for the wear of. the electrodes which previously may have occurred.

In the preferred embodiment of the invention, these wear compensating couplings are in the form of cams or wedge-shaped elements and a deviceis provided for holding them out of the way, to permit the electrodes to seat firmly against one another, after. which the wear compensators are released co-actively to couple the electrode movingmeanswith the shifter. Each pair of electrodes constituting a gap is served by an individual compensator. Therefore, whether theV machine embodies one gapor a plurality, the movement of theV shifter througha Xe-rl distance will causea predetermined gap Width to be established.

Theshifter the. preferred embodiment is actuated manuallyby a resetting .knob or lever through which. the gap` electrodes may be reset from time to. time. Most technicians, having cause to operate a knob or lever of this type, will moveitvery quickly. However, in accordance withthepresent invention, an interlock is provided to delay the couplingoflthe shifter with the Ymeans for .moving the. electrodes vuntil such time as the electrodes haveengaged.oneanother firmly andthe wear. compensating 'couplings have assumed their co-activeor operative positions of engagement. daily practice, a doctor or technician may utilize an electro-surgical machine of the type served by the present sparkgap mechanism many timesthroughout the day. Each time he does sarthe gaps readilyareresettable to insure the delivery o-electrical energy having the sameV characteristics as that provided in a preceding period of operation. Since resetting of the'gap Width proceeds from the reference condition4 invvhich the electrodes are in engagement with one another, the resetting is caused to take place conveniently as-an incident to the placing of the machine into electrical operation, andthe apparatus, therefore, is not dependent upon the special attention of the operator in respect togap adjustments.

A typical machine constructedA in accordance with these principles is illustratedzin the drawings in which:

Figure 1 is an elevation;of the apparatuslooking ati thee endet-"Which the. control. knob is located.

Figure 21is a side elevation.

Figure Y3 is atop plan-view showing the Wear compensator in various positions .Y corresponding In accordance with to the wear conditions ofthe various electrodes of the apparatus.

Figure 4 is a fragmentary top plan view showing the construction of the interlock which is effective to prevent resetting of the electrodes until the wear compensators have assumed their operative. positions.

Figure 5 is a cross sectional View taken on the line 5-5, Figure 4, showing additional details of construction of the interlock.

Figure (iis a view similar to Figure 2, but showing portions of the apparatus in section to illustrate details of construction.

Figure 'Tis a top plan view illustrating the interconnection of the electrode resetting apparatus with the interlock.

Figure /8 cross sectional View taken on the line 3--3 of Figure '7.

Figure 9 is a plan view similar to Figure 7, showing. the relationship of the partsduring a resetting operation.

Figure. l0 is a cross sectional view taken on the lineV l--Il of Figure 9.

Figure llis a cross sectional view taken on the line li--il Of Figure 9.

Figure l2 is a cross sectional view showing detail ofconstrnction of one embodiment ofa wear compensator.

Figure 13 is a longitudinal'sectionalvievv taken on the line l-IS of Figure 6, and' Figure i4 is an enlarged sectional view showing the rel'ationsl'iipk of' the parts of an electrode spacing assembly.

The Vapparatus shown in the drawings consists essentially of one' or more pairs of cooperating spark electrodes indicated generally at i and 2 which are adapted to be separated'from one another by a linkage indicated generally at 3. This linkage is actuated from a shiftermember, indicated generally at il, whichl responds in movement to the actuation of a knob or handle indicated generally at 5. The wear compensating keys, one for each pair of electrodes, are indicated generally at 6, While an interlock 'i is associated with the shifter member.

The spark gap apparatus which is herein illustrated embodies four pairs of spark electrodes connected electrically in series, and the wear compensating mechanism not only insures predetermined spacing. as to any pair of 'electrodes but also insures uniformityV of spacing from pair to pair. However, as previously described, the present inventien is adapted to be used inconjunction with a single gap machine, for the purpose of insuring accuracy in the spacing of the electrodes throughout their useful life, or-may be employed in conjunction with a plurality of electrodes different in number or arrangement from that disclosed in the drawings. It is also to be understood that the apparatus isV adapted for use in conjunction with thermo-compensating mechanism of` the type disclosed in U. S. Patents No; 1,695,157 and`1,791,464 whereby heat incidental to sparking does not eifect gap width.

In the apparatus disclosed, end plates il) and Il are traversed by support rods I2 and I3. These are arrangedin spaced'relationship to one another at`r the corners of the end plates, and are surrounded respectively by insulator tubes ifi which extend throughout their length. The rods l'and the insulator tubes pass through insulator bushings l5-at theY eXterior'aces of the end plates lil and l I, andportions ofthe support rods extending-beyond the bushings are threaded tocarry nuts iwhich' bear'on *washers* I7 At spaced intervals intermediate the end plates I0 and II, the insulator tubes I4 pass. through another by insulator bushings 23, preferably of ceramic material. Each radiator 23 is in electrical interconnection with the radiator 2l of the next gap through an electrically conductive bushing which has its endwise portions bearing racially against the respective radiator plates. Radiator 29 of the pair at one end of the series is in electrical connection through a conductive bus strap 26 which is mounted over insulator tube I4. This strap in turn is insulated from the adjacent end plate I by means of a ceramic insulator bushing 2I. Radiator 2| at the opposite end ofthe series is in electrical connection, through an electrically conductive bushing 28, with a bus strap 29 which, in turn, is insulated from the adjacent end plate II by means of an insulator 30. The spacers and bushings and radiators occupy the entire length of the tubular insulators I4 between the end plates and it will be seen therefore that the nuts I6 serve to clamp all of these members into rigid assembly. Terminal straps 26 and 29 project sidewisely from the assembly where they are bent to facilitate interconnection of electrical leads to the apparatus.

The upper portions of the radiator plates 23 are free and these plates are therefore bendable or yieldable. For convenience, they may be termed movable radiators. However, these plates are provided with edge flanges 3| since it is preferable that they be made of copper for oonductive and radiating purposes and might tend to lose their resiliency over a period of time.

On the other hand, radiator plates 2I extend upwardly beyond the edges of the movable radiators and are traversed at their upper portions by spaced tubular insulators 33, which carry draw rods 34 having nuts 35 at their endwise portions, similar` to those at the bottom of the machine. Spacing insulators 33 extend respectively over the insulator tubes 33 between the respective radiators, and between the end plates .and the next adjacent radiators, to hold them vall in fixed spaced relationship to one another.

Each radiator 2I carries a spark electrode 3'I and each movable radiator carries a cooperating spark electrode 38. The faces of these electrodes are preferably crowned, as shown in Figure 2, and they are of such length that they normally engage one another when the movable radiator yplates are in relaxed position. However, these electrodes, during operation of the mechanism are spaced apart for the emanation of sparks between them. From the electrical interconnections previously noted, it will be seen that current may pass from one of the terminals 26 or 29 through the radiator plate which is in connection with it, to its electrode, then across the gap to the adjacent electrode, from this through a conductive bushing to the next radiator and gap, and so on through all of the gaps to the lother terminal.

Any suitable mechanism may be employed for moving one or both of the electrodes such that they may be spaced appropriately one from another. In the embodiment of the invention shown in the drawings, the linkage 3 is employed for this purpose, to force the radiator plates 2U away from the stationary radiators 2l and thereby separate the contacts. Thus. the stationary radiators 2I are .equipped with bracket pieces 33,

`igurated to urge the balls seated which are spaced from one another to provide a clevis which carries a pivot rod 43. The latter is held against axial displacement by collar washers 4I. Pivot 4l? passes through. levers 42, one lever for each gap, and, above each bracket 39, each stationary radiator carries a guide bushing 43 which may be press fitted into place, as shown in Figure 14. This bushing in each gap assembly is bored to receive a driving pin 44, having one crowned end bearing against lever 42 while an opposite crowned end bears against the face of a ceramic insulating button 45. The button has a shank portion which is press fitted into a bore in the adjacent movable radiator plate 2I. As the lever is moved it pushes the pin 44 which in turn pushes the movable radiator 23 away from the stationary plate 2I and thereby separates the electrodes 3'I and 38 which are carried respectively by the radiators.

The resilience of the movable radiator plates is probably adequate to return electrodes 3l and 38 into engagement with one another when the lever 42 is i'ree. However, as an extra precaution, such return positively may `be effected by the supplemental mechanism which is shown in Figure i4. rThis consists of a draw rod 48 which passes through insulator bushings 49 and 5i) mounted at opposed faces of the respective radiator plates 23, 2l. rlhe draw rod has heads 5i, 5i at its ends, these being engageable with the outer faces cf the bushings 48 and A compression spring 52, surrounding the rod 48, has one end seated against the face of bushing 53 while the opposite end bears against a washer 53 which abuts the adjacent head 5I of the rod. The spring is compressed when the electrodes are separated, and therefore urges them to engaged position.

The end plates l) and I I are flanged outwardly at their upper edges, as at 55 (Figures 2 and 6). Elongated angle members 56, arranged in spaced parallel relationship to one another, extend across the end plates I and Il, and are fastened in place on the respective endwise flanges 55 by means of screws 51, carrying washers 53 and nuts 59.

The upstanding walls of the angle members 53 constitute guides for the shifter member indicated generally at 4. This, preferably, is in the form of a channel Si), of such width that its side walls extend upwardly adjacent the upstanding ilanges of the angle members 55. For guide purposes, the vertical walls of the angles 56 have grooves or depressions El provided at their inner faces. These are in longitudinal alignment with one another and they provide linear races for ball members 62. One side wall of channel contains recesses 63 for supporting the balls in engagement with the cooperating guide grooves 5I. However, the other side of the channel member 6i) carries resilient leaves 64 which are contherein toward the adjacent guide grooves (Figure 8). This construction provides substantially frictionless movability of the shifter member 53, and at the same time eliminates any sidewise looseness in the assembly. Shifter channel 63 is slotted longitudinally as at G3 and the upper endwise portions of the linkage levers 42 extend through the slots.

An elongated bracket 65 is mounted at the bottom face of one of the angle members 55 to mount a plurality of leaf springs 5l', which are fastened as at 6'8 and which extend resiliently into engagement with the edges of the levers 42 near the upper portions thereof. The springs 'atraen-f 'serfvetoY holdsV the'levers .against` the push` rods M'gzsuch-that the. various-,parts ofsithe sparkgap separating linkage are: always operativ'e: without loss ofv motion.

The shifter. 4, constitutedbyV channel 6.01m. the embodiment disclosed, .occupies two different functional.' positions correspondingv respectively to operative* spacing and. non-operative vengagement:ofl the .spark electrodes. In.; the Vpresent apparatus, it' is moved/manually ,to4 operative position: and 'is returned orH retracted, by `spring pressure, althoughf an. opposite construction is equally suitable. The-details oftheman'ualilactiiator; appear atalater. point. The details of the retracting apparatusl areas follows.:A

One endplate, Iii, of the assembly, is equipped with amounting bar iii',whichY projects upwardly Vbetween the` angles E6; as shown in'. Figure 7,

through a slot or openingp'iin the bottom web of the shifternchannel 63. Within the channel area, the mounting'bar carries a screw 'l'which extends longitudinally of .theshifter bar.. This. screw is held in xedpositiom once adjusted,fby means of a lock nut which binds against the face ofthe mounting bar 'l'into which thescrew is thread ed. The shifter channel 59', carries an arm 16, which'is slotted so; as to clear. the screw shank, and.: aV compression. spring. '11, surrounding the shankk of the screw, has its one end abutting the lock nut 15 while the' other Yabuts awasher 'i8 whichin turnbears'facially against the arm i6 of the shifter channel. Hence, the compression spring always urges the shifter toward its retracted position, butsuch movement Vis limited byabutment ofthe arm i8 against the lheadof the screw "M, This screw maybe adjusted to vary the point at whichzthe shiftercomes lto rest on the point from which it is caused tomove in opposite direction;

Ani operating rod 89 extends alongan outer face of an end plateof the apparatus andthrough a suitable opening 8l in the bottom'webf of the shifter channel. The. shaft is rotatably journalledin bores provided in arms 82 and 83 of a bracket Ywhich is mounted on the end 1 plate Vof the assembly, the bracket being fastened by screws 85 which pass through theend plate into threaded engagement with'bar 'iE-at the inside of the endv plates so as tohold both in fixed position. Collars 3%, 86 are provided on the shaft at opposite sides of one of the arms, 83, andthe shaft also passes through a guide. bushing. 87 which is xedupon thefother of the bracket ears 82. rlhis shaft, there-fore,4 isrotatable .in the arms of the bracket andfis held againstv longitudinal displacement.

Intermediate the side walls ofthe shifter. channel Sa, the operating shaft 8@` carries a-shifter cam 8S congurated to provide a throw portion 89 at a-portion of its periphery while the balance of. theY periphery includesv a...nonfoperative dwell. The cam cooperateswitha roller shaped follower Si which is rotatably.I mountedupon a studv 92 projecting from the bottom. web of the shifter where it is held by means of a nut93. Whensthe shifter is in.. retracted position, normally, the dwell portionof: the earn` is just outof engagement with the follower; that is, when the armil of the shifter isin abutment with the vhead ofthe screw` lll. 5, which isxedzto therod .30,.willcausethe throw 89r of the cam to engage the roller and move the shifter against thebias'ofspring "il,

Motion of the shifter, in -.the manner justvdescribed for-by other.suitable means; is transmitted However, rotation: of. vactuating knob to v'the'sparli gap linkage. levers 42 throughthe wearcompensators or keys* indicated generally.l at E; Itis the function of these elements to provide (zo-'active engagement between the Ashifter-'mennber andthe spark gap linkages, but also to discriminatively adjust themselves to compensatefor wear. whichhas occurred upon the electrodes.

The. wear compensators or keys of the present apparatus function to provide a uniformity ofspacing atv all times,` whether one orv a plurality ofsfspark;gapsiarexemployed in the mechanism by. couplingithe shifterwith'the electrode spacer linkagewhen the: electrodes are in the reference condition. in which: they 'engage one another. In

Atheembodiment disclosed V'in'. the drawings, the

wear. compensators.are'provided' for each pair of electrodes; andthese units are-in the form of selfadjusting or discriminating cams or wedges `which are carried by the shifter, but which are biased to moveinto engagement with the levers 42 when they are permitted todo so, and when the levers are in positions corresponding to engagement of the electrodes. Each compensator mechanism, asshown' in Figures '7 andll, comprises a stud locatedin the shifter channel 60 between the side walls thereof, and extending into threaded engagement with a T nutcongurated` to fit'the slot E9 in the bottonrweb. of the -shifter channel. The stud 95 carries a nut 96 which bears upon. a washer 9i at the one face of the channel web for locking the stud, inianyposition of initial adjustment, against the T nut 94 at the. other side 0f the channel. Stud Q5: in eachY compensator assembly carries. a: washeri 98""adjacent its head,- and-'a spool. 99 is rotatably mounted upon the'stud'between: the washer 98; and another washer 99u, which1isadjacent the' face of the lock` nut 96; A compensator cam` l. is fixed' to the spool 99, as disclosedr in.Figure 12. Thecam i-s generally of spiraliconguration, made of light weight mate'- rial .and has a flange |61 bent up Yfrom its outer peripheryl tov provideV anoperating face of adequate width;

A hairz-type spring l02 is wound' around the spoolof leach assembly andoneend of the spring is hookedto the cam, as at' H13, while the opposite endzof the spring is'` hookedthrough an ear |04, bentA laterally fromvan .edgewise portion of the shifter channel S0. The spring,'therefore, inthe arrangement shown, biases the cam in counter clockwise direction.

The compensatorrassemblies just described are arranged respectively, adjacent'linkage levers 42 whereby the edges'of the cams are engageable with the edges of the linkage levers at the portions ofthe latter whichproject through the slots 69 inthe shifter channel 65. It is to be noted that thek cams are so Apositioned on the shifter that the ladsor'portions of -least radius are spaced slightly away fromV the edges of the linkage levers 42 whenthe levers are in positions correspondingto engagementofv the electrodes; For convenience, this maybe termed .the starting positionof. the shifter, or the non-operating. position of the mechanism'.

When a compensator i is allowedto adjust itself 'under'the iniiuenceofits actuating spring 4t2, itwill move until its periphery,vwhich is of gradually increasing radius, engages the edge of linkage lever r 52,! which v-itserves' thereby operatively couplinglthelever with the shifter.` The cam actuating spring is of course incapable of driving the cam-beyond this point againstthebias ofspring v52,01 against the resilience ofthe radiator -plates'ilg 'regardlessrof the compounding of forces which is provided in the linkage system. In other words, each cam rotates until it assumes a position of working engagement with the lever, without actually moving the lever.

When the compensator cams key the levers to the shifter in the manner just described, movement of the shifter will effect uniform movement of all of the levers and, therefore, all of the electrodes will be separated uniformly. Since the throw of the cam shifter 3B causes movement of the shifter through a predetermined or xed distance, each, or all, of the electrodes will be spaced a distance which is the same as, or proportional to, such xed distance, depending upon the nature of the linkage system. In the machine shown, the ratio of movement in the linkage system is approximately to l. The spark gaps desirably are approximately .001 inch in width, and the cam throw is such that the shifter moves the upper ends of the lever approximately .005 inch. The ratio, of course, readily may be varied to suit the intended construction and to suit the gap widths to be employed.

It is desirable, as an incident to resetting,r of the mechanism, to disengage the compensating cams from the l-evers, so that the levers, being released, will permit the electrodes of each pair to come to rest in full engagement under the biasing forces which urge them together. For this purpose, a cam shifter is utilized which, in the preferred construction, is actuated from the control knob 5 when the latter is moved toward off or non-operating position, that is, when it is moved in a clockwise direction in the apparatus illustrated. The cam shifter is in the form of an elongated bar IIB (Figures 9 and 11) which extends along the bottom web of the electrode shifter channel 6B. This bar is guided longitudinally, at its one end, by a screw III, which passes through a suitable slot I2 in the bar into threaded engagement with the bottom web of the electrode shifter channel Si). The other end of the cam shifter IIIB, carries a square or rectangular guide boss as indicated by the dotted lines I I3 in Figures 3 and '7, which rides in a slot I I4 cut into the shifter channel ISB. Cam shifter bar I'I includes a longitudinal upstanding ange H4, to which a series of fingers |I5a are fastened by means of screws Il and nuts I I1, one finger for each wear compensating cam'. These ngers project laterally from the cam shifter bar for engagement with respective shoulders |20 which are provided on the wear compensating cams I Ii, intermediate the lead and terminal portions thereof. The fingers IIEa also are of a somewhat elongated nature to provide faces IIB against which the endwise portions of the cam shoulders rest after the cams have been backed-away or shifted to their starting lpositions by the fingers.

The cam shifter bar II is moved, to accomplish these functions, by means of a lever arm |22 (Figure 4) fastened upon the control rod 863 so as to swing with it and thereby cause the arm to engage a stud I24 projecting from the shifter bar. Arm' |22 is located upon the shaft BIJ against a bushing 25, the latter having its opposite end located adjacent the operating rod guide bushing 81. Rotation of the control knob 5 causes the lever |22 to push the stud and move the cam shifter bar longitudinally in its guide slots ||2 and I I4. When the shifter bar Il@ is actuated in this manner, the ngers I|5a engage the cam shoulders |26 and thereby rotate the cams in the direction effective to cause their peripheries to back away from the linkage levers 42. The cam shifter bar is urged in an opposite direction by means of a tension spring |28 having one end hooked to an ear |23 projecting upwardly from an end of the main shifter channel 60, and its opposite end hooked to an ear |30 of the cam shifter bar. Retracting movement of the cam shifter bar, when permitted, is limited by abutment of the end of the bar against the ear |28.

The relative `position of the parts when the fingers II5a are holding the cams in their retracted or starting positions is shown in Figure 9. When the lever I 22 releases the stud` |25, the shifter bar moves backwards and the cams start to rotate, the shoulder surfaces |20 thereof relatively following the fingers H5. The cam peripheries thus approach and eventually engage the linkage levers.

Control knob 5 conveniently serves both the main shifter channel 6B and the secondary shifter III) carrying the fingers I Ha by which the wear compensators are retracted and released, the parts being so arranged that these motions occur sequentially, whereby the shifter channel 8G is moved after the compensators are released.

The control knob 5 manually may be moved very rapidly; in fact, the average operator tends to reset the mechanism by giving this knob merely a sharp twist in the proper direction. Such rapidity of movement may cause the actuation of the shifter BD before the levers have assurned rest position, or before th-e compensating cams have reached operative positions of engagement with the levers. In this event, the full compensating function of the apparatus would not be exercised. However, the interlock mechanism, indicated generally at 1, is utilized to avoid this circumstance by preventing the actuating knob from moving the shifter until a momentary period of time has been allowed to elapse during which the compensating cams are moving into position.

In the preferred embodiment, in this respect, a dash-pot cylinder |32 is mounted on a bracket |33 (Figures 1, 2 and 6), the bracket being fastened in place by the same screws 85 which hold the bracket 84 for the operating lever 80. The dash-pot carries a piston |35 which is mounted at the end of a piston rod |38 having spaced collar washers |31, |31 at its outer endwise portion. An ear |38, mounted on the bottom of th-e bar IIB, engages the piston rod |36 intermediate the washers |31 to interconnect the bar IIQ with the dash-pot device. The dash-pot causes the cam shifter bar I I D to move slowly, under the inuence of spring |28, and during such movement, the compensating cams gradually assume their operating positions.

In addition to the apparatus just described, the interlock compris-es a lever I4I] which is rotatably mounted on the operating rod 88, but operated by it through lost motion connections. Thus, lever |40 comprises two arms I4| and |42 projecting from the operating rod in opposite directions. Cam shifter member IIII carries an interlock obstruction wall |43, which is movable with it, and one of the arms |4| of the lever i452 is equipped with a tail |44 projecting from its outer extremity that engages or abuts the obstruction wall when the lever is swung, unless the movement of the cam shifter II IJ has been such that the tail 144 may pass the end of the obstruction.

Lever |40 is moved from the operating rod 8|) by means of a pin |625 extending from the lever |22, which, as previously described, is xed to the operating rod. This pin bears upon an edge of the arm |42fof the lever |45 to carry the latter with it. In this manner, the tail |594 is caused to approach the obstruction wall |43 as the knob 5 is rotated. Bearing in mind that rotation of the knob 5, in'counterclockwise direction in the construction illustrated, will rst release the shifter bar I and only then cause the throw 89 of the main shifter cam to engage the follower 9| and thereby move the shifter 60, it will be seen that the tail |134 will hit the obstruction wall |3 unless the `compensator shiftelr ||0 has reached itsreleaseposition. Its relatively slow movement in this direction, as' controlled by the dash-pot, allows ample time for the wear compensators to reach their positions of engagement with levers E2. Of course, when the tail hits the wall |23, further movement of the knob is prevented, and actuation of the shifter 65 by cam throw 89 is withheld.

Arm M2 of the lever lflll has its endwise portion congurated to -constitute a latch |56 positioned for cooperation with an ear Ml carried by the cam shifter H0, so as to hold the shifter Ill in advanced position in which the wear compensators are backed away from linkage levers 42. Lever MB is biased so that'the arm |42 is normally in latching positiony by means of a spring member |48 which is lcoiled about a spool |29, the latter being xed upon'the face of lever |42 and supported by the operating rod Sil. One end of the spring |48 is hooked upon the lever Idil, while the other is hooked to an ear |59 bent from the side wall of the shifter channel 5|). As the operating rod 35 is moved by knob 5, pin M5 on the arm |22 swings the latch arm |62 toward unlatching position at the same time that the tail |45 approaches the obstruction wall |453. 'Counter rotation of lever |45, under ythe Vinfluence of spring m8, is limited by abutment of the rear edge of arm IM against the follower roller 9|. As the camshifter ||0 is advanced by mea-ns of the .arm |22vpushing upon the pin |24, the shifter latches itself so as to remain in advanced position until released by counter rotation of knob 5.

When the mechanism is idle, the parts are in thev 'relative positions shown in Figure 9, the shifter bar Hi) is latched, as ljust described, and the cam'actuating fingers Ha, have backed the compensator cams Yaway from the linkage levers 42. TheV electrodes are engaged with one another, and some of the levers d2 are in different positions than others, depending upon the extent to which the electrodes-have 4been previously Worn away. At this time, .the shifter SEI is in its idle or rest position, to which it has been driven by compression spring l1.

Rotation of the knob 5 at this time, in counterclockwise direction in the illustrated apparatus, causes the lever |22 to swing until 'its pin |55 reaches the edge of the arm |i2 of lever it. During this phase of movement, the cam 'shifter bar H0 is not moved by spring |28, because the bar is latched. However, further rotation-of the knob 5 vin the same directionoauses the pin |25 to carry the latch-arm |42 with it and thereby release thecamshifterbar Ill, which now moves relatively slowly under the control of the dash pot. These rotational-movements of the operating shaft have meanwhile caused the throw 39 of the main shifter cam to approach the follower 9|, but not yet to move it.

Asthefshifter bar ||`0 recedes, the lingers ||5a recedefrom the shoulders |25 ofthe compensating/cams, and earns` rotate under the influence of the springs |521su'eh'that their peripheries approachand move into engagement with the edges of the-levers 42. At this time, th'cams will perhaps bein different positions, as shown in Figure 3, A'corresponding to Ythe'extent to which the wear of electrodes has allowed the different linkage levers to occupy different positions when the electrodes are engaged. The shiiter is, therefore, now operatively kcoupled with the levers. Continued rotation of the actuating knob `5 causes the throw 89 of the shifter camfto engage'the follower 9| and, therefore, the main shifter 6B simultaneously drives all of the levers :i2 -and spaces the electrodes accordingly.

'If the knob 5 is moved very rapidly from the starting `position shown in Figure 9, then the latch |l|2willy release the cam shifter bar il), but the tail |154 of the interlock |5| will come into abutment with the obstruction |53 and further rotation of the knob will be 'prevented until the cam shifter lever has been allowed to complete its movement. After this, the tail Mil rma-y pass the obstruction to cause the actuation ofthe main shifter 55 by cam 88. Forceful twisting of knob '5 may actually `preverrt longitudinal movement of the cam shifter bar because of the frictional engagement 'of the tail Mill' lwith the obstruction wall, and this condition rwill prevail so long as the operator continues to hold the knob with such force. However, as soon as the knob is released, the shifter barnfwill move on, and the operator then is at liberty to continue the rotation and reset the gaps.

Upon completion of the resetting operation, the parts are in the relationship shown in Figure 7. At this time, the apparatus is ready to be operated electrically, and all of the gaps are of the desired width.

Movement of the control knob 5 in an opposite direction, i. e. clockwise, rst causes the tail IM to return over the end of the obstruction wall |153. The follower 9| reaches the dwell of the cam 88 and as it does so, the shifter 6o recedes under the influence of the spring ll. This permits the levers G2 to follow the wear compensating cams and allows the electrodes to approach one another, although at this particular phase of the operation, not all of the electrodes may be in actual engagement since some may have been worn in the preceding operation. Further rotation of the knob in the clockwise direction causes the arm |22 to approach and engage the stud |25 on the cam shifter bar |53, thereby advancing the nngers ||5a until they cause disengagement of the wear compensating cams with the levers 2. Therefore, this movement releases the levers completely, and allows all of the electrodes to come lirmly into engagement .with one another. Shortly after this occurs, the latch M2 is actuated to engage the ear Ml? and thereby hold the shifter Mil. Continued movement in this direction is prevented through abutment of the end of the slot ||2 with the stud At this time, the parts are in the position shown in Figure 9.

From the operation of the apparatus just described, it may be observed that a plurality of electrodes accurately may be spaced from one another uniformly regardless of their wear, and such accuracy may be maintained through the periodic resetting of the mechanism whereby the desirable conditions of uniformity are re-established'to compensate for any electrode deteriora- 13 tion that may have occurred in a preceding period of operation. On the other hand, the same principles conveniently may be utilized in a single gap apparatus to re-establish, from time to time, optimum gap spacing for it.

Having described our invention, we claim:

l. A spark gap mechanism comprising; a pair of electrodes normally engageable with one another, means for separating the electrodes such that a spark gap is delineated therebetween, a shifter, means for moving the shifter a fixed distance, and a wear compensating member for coupling the shifter with the said electrode separating means when the electrodes are in engagement, whereby subsequent movement of the shifter through the xed distance separates the electrodes a predetermined distance.

2'. Spark gap mechanism comprising; cooperable spark electrodes normally engaged and being separable, linkage effective for separating the electrodes, a shifter, and a self-adjusting wear compensator biased to assume different positions of coactive engagement with the shifter and the linkage, depending upon the wear condition of the electrodes when the linkage is in a position corresponding to engagement of the electrodes, the said wear compensator being effective for transmitting shifter motion to the linkage, whereby movement of the shifter through a predetermined distance effects spacing of the electrodes a predetermined spark gap distance.

3. Spark gap mechanism comprising; cooperable spark electrodes normally engaged and being separable, linkage effective for moving one of the electrodes from the other, a shifter, means for moving the shifter a predetermined distance, a key biased to assume different positions of coactive engagement with the shifter and the linkage, depending upon the wear condition of the electrodes when the linkage is in position corresponding to engagement of the electrodes, and an interlock for rendering said shifter moving means ineffective until said key has assumed a position of coactive engagement with the shifter and the linkage.

4. Spark gap mechanism comprising; radiators carrying cooperating spark electrodes which are engageable with one another, a linkage effective for moving at least one of the radiators to thereby separate the electrodes, a shifter common to said linkage, and a self-adjusting key carried by the shifter, the said key being constructed to assume different positions of coactive engagement with the linkage, depending upon the wear condition of the electrodes of the respective pairs when the electrodes of the respective pairs engage one another, and means for moving the shifter through a predetermined distance whereby such motion is transmitted through the key and linkage to the movable radiator for spacing the electrodes a predetermined spark gap distance.

5. Spark gap mechanism comprising; cooperable spark electrodes normally engaged and being separable, linkage effective for separating one of the electrodes from the other, a shifter, means for moving the shifter a predetermined distance, and a self-adjusting wear compensator biased to assiune different positions of coactive engagement with the shifter and the linkage, depending upon the wear condition of the electrodes when the linkage is in position corresponding to engagement of the electrodes with one another, whereby movement of the shifter causes the linkageto move one electrode from the other,

through the wear compensator, for spacing the lelectrodes a predetermined sparkgap distance.

6. Spark gap mechanism comprising; a plurality of pairs of cooperable spark electrodes normally engaged and being separable, linkages effective for separating the electrodes of the respective pairs, a shifter common to all linkages, self-adjusting wear compensators, one for each linkage, the said wear compensators being biased to assume different positions of coactive engagement with the shifter and the respective linkages, depending upon the wear conditions of the electrodes when the linkages are in positions corresponding to engagement of the electrodes, the said wear compensators being effective for transmitting shifter motion to the linkages, whereby movement of the shifter through a predetermined distance effects spacing apart of the electrodes of the pairs through a uniform predevermined spark gap distance.

7. Spark gap mechanism comprising; a plurality of cooperable spark electrodes arranged in pairs, the electrodes of each pair being normally engaged and being separable, linkages one for each pair of electrodes, for separating them, a shifter common to all of the pairs of electrodes, and self-adjusting keys for each pair of electrodes, the said keys being biased to assume different positions of coactive engagement With the shifter and the linkages respectively, depending upon the wear conditions of the electrodes when the linkages are in different positions corresponding to engagement of the electrodes of the respective pairs, whereby movement of the shifter through a predetermined distance effects spacing of the electrodes of the pairs a predetermined spark gap distance which is uniform in respect to all of the pairs of electrodes.

8. Spark gap mechanism comprising; electrodes normally engaged but separable to dene a spark gap, a lever for moving one of the electrodes from the other, a shifter, means for moving said shifter through a predetermined distance, a self-adjusting key for coupling the shifter and the lever when the lever is in position corresponding to engagement of the electrodes, a time delay device for rendering said shifter means ineffective until the said key has coupled the shifter and the lever.

9. Spark gap mechanism comprising; spark electrodes normaly engaged when the mechanism is idle and a resetting device for separating one electrode from the other a predetermined spark gap distance comprising, a lever for separating the electrodes, said lever assuming different positions when the electrodes are engaged, depending upon the wear condition of the electrodes, a shifter movable through a fixed distance, and a self-adjusting wedge adapted to position itself in coactive engagement with the shifter and the lever when the lever is in closed electrode position, whereby subsequent movement of the shifter through the predetermined distance will cause separation of the electrodes a predetermined distance independently of the wear condition of the electrodes.

10. Spark gap mechanism comprising; a plurality of pairs of spark electrodes connected in a series, the electrodes of the pairs normally being in engagement when the mechanism is idle, at least one electrode of each pair being movable, a shifter common to the movable electrodes of the plurality for moving them in unison, and means for moving the movable elecatraer? trodes=of the plurality from engaged position a fixed distance which isvcommon to them all.

11. Spark gap mechanism comprising; a plurality of pairs of spark electrodes connected in a series, the electrodes of the pairs normally being in engagement when the Vmechanism is idle, at least one electrode of each pair being movable, a shifter common to the movable electrodes of the plurality for moving them in univ son, and means for moving the movable electrodes of the plurality from engaged position a fixed distance which is common to them allgsaid means including self-adjusting wear compensators, one for each pair of electrodes, said wear compensators being eective to couple the shifter with the movable electrodes after they have engaged one another.

12. Spark gap mechanism comprising; a pair of cooperating spark electrodes normally engageable, a shifter movable through a predetermined distance, means for moving the shifter through said distance, andmeans for 'separating the contacts including a self-adjusting key responsive to the movement of the shifter and effective for separating the contacts from engagement a predetermined distance proportioned tosaid first named predetermined distance.

13. A Yspark gap mechanism comprising; a pair of electrodes normally engageable with each other, means for separating the electrodes to form a spark gap therebetween, a primary shifter, a wear compensating member on said shifter for coupling the same to said electrode separating means when the electrodes are in engagement whereby movement of the shifter separates Athe electrodes a predetermined distance, a secondary7 shifter movable relative to the primary shifter and engageable with said gear compensating member to retract the member out of engagement with the separator means when the electrodes are in engagement to reset the compensating members, a common actuating shaft connected to said primary and secondaryvshifters, and arranged `to be manually rotated to actuate the Shifters, said actuating shaft being operable to actuate the primary shifter to separate the electrodes when the shaft is rotated in one direction and operable to actuate the secondary shifter to retract the compensating members when theY shaft is rotated in the opposite direction.

14.. A spark gap mechanism comprising; a pair of electrodes normally engageable with each other, means for separating the electrodes to form a spark gap therebetween, a primary shifter, a wear compensating member on said shifter for coupling the same to said electrode separating means when the electrodes are in engagement whereby movement of the shifter separates the electrodes a predetermined distance, a secondary shifter movable relative to the primary shifter and engageable with said wear compensating member to retract the member out of engagement with the separator means when the electrodes are in engagement to reset the compensating members, a common actuating shaft for said primary and secondary Shifters, a cam on said shaft connectedfto the primary shifter to actuate the same, a lever arm on said shaft engageable with the secondary yshifter to actuate the same, said cam being operable to actuate the shifter to separate the electrodes when the actuating shaft is rotated in one direction and said lever arm being operable toactuate the 'secondary shifter to -retract the com;-

1-'6 pensating members when lthe shaft `is rotated in the opposite direction.

15. A spark gap mechanism comprising; a pair of electrodes normally engageable with each other, means for separating the electrodes to form a spark gap therebetween, a'fprimary shifter, a wear compensating member on said shifter for coupling the same to said electrode separating means when the electrodes are in engagement whereby movement of the shifter separates the electrodes a predetermined distance,v a secondary shifter movable relative to the primary'shifter and engageable with said Wear compensating member to retract the member out of engagement with the separator means when the electrodes are in engagement to reset the compensating members, a common actuating shaft connected to said primary and secondary shiftersand arranged to be manually rotated to actuate :the Shifters, said actuating rshaft being operable to actuate the primary shifter to-separate the'electrodes when the shaft is rotated in Vone direction and operable to actuate the secondary shifter to retract the compensating members when the shaft is rotated in the opposite direction, latch means engageable with the secondary shifter to .latch the shifter in retracted position, and a latch release member on said shaft engageable with the latch means to release the secondary shifter when the actuating shaft is rotated in thegdirection to separate the electrodes.

16. A spark gap mechanism having respective pairs of spark gaps constituting movable and stationary electrodes and having a primary shifter connected in common to all 'of vsaid movable electrodes, means for establishing a wear compensating connection between the primary shifter and the movable electrodes, a secondary'shifter arranged to reset said wear compensating means, an actuating shaft common to said primary and secondary Shifters, a cam secured'upon said shaft, a cam follower secured upon said primary shifter, said cam having a throw adapted to -retract'the primary shifter to separate the electrodes lwhen the actuating shaft is rotated in one direction, means on said actuating shaft engageable with said secondary shifter to retract the same to reset the wear compensator means when the actuating shaft is rotated in the opposite direction with the electrodes in engagement, a latch arm engageable with the secondary shifter to latch the same in retracted position when the actuatl ing shaft is rotated to the limit of its retracting movement, spring means for urging said sec,-

ondary shifter in the opposite direction, and a trip member on said shaft engageable with saidlatch member to release the secondary shifter when the shaft is rotated in the opposite direction.

17. Spark gap mechanism comprising; respec'-, tive pairs of electrodes, one electrode of each pair being stationary and the other being movable relative to the first, a respective lever operatively connected to each of said movable electrodes, a primary shifter for actuating said respective levers unitarily in a direction to separate said respective electrodes to form a spark gap, a wear compensating key for each of said levers mounted on said primary shifter for coupling the shifter to the respective ievers when the shifter is in a position corresponding to engagement of the respective electrodes, a secondary shifter mounted for longitudinal movement relative to the primary shifter, means on said secondary shifter for engagingsaid'compensating keys to retract said keys toresetthe same when the primary'shifter is in electrode engaging position, an actuating shaft common to the primary and secondary shifters, a cam fixed on said shaft, a cam follower xed on said primary shifter engageable with said cam to shift the primary shifter in electrode separating direction when the actuating .shaft is rotated, and a shifter arm secured to said actuating shaft and engageable with said secondary shifter to shift the same in key retracting direction when the actuating shaft is rotated in the opposite direction, said cam having a dwell portion for maintaining the primary shifter in electrode engaging position during rotation of the actuating shaft in key retracting direction.

18. Spark gap mechanism comprising; respec tive pairs of electrodes, one electrode of each pair being stationary and the other being movable relative to the first, a respective lever operatively connected to each of said movable electrodes, a primary shifter for actuating said respective levers unitarily in a direction to separate said respective electrodes to form a spark gap, a wear compensating key for each of said levers mounted on said primary shifter for coupling the shifter to the respective levers when the shifter is in a position corresponding to engagement of the respective electrodes, a secondary shifter mounted for longitudinal movement relative to the primary shifter, means on said secondary shifter for engaging said compensating keys to retract said keys to reset the same when the primary shifter is in electrode engaging position, an actuating shaft common to the primary and secondary Shifters, a cam fixed on said shaft, a cam follower fixed on said primary shifter engageable with said cam to shift the primary shifter in electrode separating direction when the actuating shaft is rotated, and a shifter arm secured to said actuating shaft and engageable with said secondary shifter to shift the same in key retracting direction when the actuating shaft is rotated in the opposite direction.

19. A spark gap mechanism having respective pairs of spark gaps constituting movable and stationary electrodes and having a primary,

shifter connected in common to all of said movable electrodes, means for establishing a wear compensating connection between the primary shifter and the movable electrodes, a secondary shifter arranged to reset said wear compensating means, an actuating shaft common to said primary and secondary Shifters, a cam secured upon said shaft, a cam follower secured upon said primary shifter, said cam having a throw adapted to retract the primary shifter to separate the electrodes when the actuating shaft is rotated in one direction, a shifter arm on said actuating shaft engageable with said secondary shifter to retract the same to reset the wear compensator means when the actuating shaft is rotated in the opposite direction with the electrodes in engagement, a latch arm engageable with the secondary shifter to latch the same in retracted position when the actuating shaft is rotated to the limit of its retracting movement, spring means for urging said secondary shifter in the opposite direction, dash pot mechanism for controlling said spring urged movement, and a trip member on said shaft engageable with said latch mem-ber to release the secondary shifter when the actuating shaft is rotated in the direction to separate the electrodes.

20. A spark gap mechanism comprising; a pair of electrodes normally engageable with each other, means for separating the electrodes to form a spark gap therebetween, a primary shifter, a wear compensating member on said shifter for coupling the same to said electrode separating means when the electrodes are in engagement whereby movement of the shifter separates the electrodes a predetermined distance, a secondary shifter movable relative to the primary shifter and engageable with said wear compensating member to retract the member out of engagement with the separator means when the electrodes are in engagement to reset the compensating members, a common actuating shaft connected to said primary and secondary shifters, and arranged to be manually rotated to actuate the Shifters, said actuating shaft being operable to actuate the primary Shifter to separate the electrodes when the shaft is rotated in one direction and operable to actuate the .secondary shifter to retract the compensating members to a resetting position when the shaft is rotated in the opposite direction, mechanism for returning the secondary shifter at a controlled rate when the shaft is rotated in the direction to separate the electrodes, and an interlock on said shaft to lock the same against rotation until the secondary shifter has returned from the resetting position to prevent separation of the electrodes until the wear compensating member has reestablished a coupling between the primary shifter and the electrode separating means.

21. A spark gap mechanism having respectivo pairs of spark gaps constituting movable and stationary electrodes and having a primary shifter connected in common to all of said movable electrodes, means for establishing a wear compensating connection between the primary shifter and the movable electrodes, a secondary shifter arranged to reset said wear compensating means, an actuating shaft common to said primary and secondary Shifters, a cam secured upon said shaft, a cam follower secured upon said primary Shifter, said cam having a throw adapted to retract the primary shifter to separate the electrodes when the actuating shaft is rotated in one direction, a shifter arm on said actuating shaft engageable with said secondary shifter to retract the same to reset the wear compensator means when the actuating shaft is rotated in the opposite direction with the electrodes in engagement, a latch arm engageable with the secondary shifter to latch the same in retracted position when the actuating shaft is rotated to the limit of its retracting movement, with the wear compensating means in resetting position, a trip member on said shaft engageable with said latch member to release the secondary shifter when the actuating shaft is rotated in the direction to separate the electrodes, mechanism for returning the secondary shifter at a controlled rate when the trip member is released and an interlock on the actuating shaft to lock the same against rotation until the secondary shifter has returned from its resetting position to prevent separation of the electrodes until dthe wearcompensating means have restablished a connection between the primary shifter and the movable electrodes,

22. A spark gap mechanism having respective pairs of spark gaps constituting movable and stationary electrodes and having a primary shifter connected in common to all of said movable electrodes, means for establishing a wear compensating connection between the primary shifter and the movable electrodes, a secondary shifter arranged to reset said wear compensating means, an actuating shaft common to said primary and secondary Shifters, a cam secured upon "lsaid shaft, acam follower secured upon said 'f primary shiiterg'said cam having a throw `adapted l'toretract thev primary shifter to separate the "electrodes when the actuating shaft is rotated l in' one direction, a shifter arm on said actuating shaft. engageable with said secondary shifter to retract the same to reset the Wear compensating -means when the actuating shaft is rotated in.' the opposite direction with the electrodes in en- "gagement7 a latch arm engageable with the secondary shifter to latch the same in retracted position when the actuating shaft is rotated Wto" the limit of its retracting movement, a trip 'member on said shaft engageable with said latch member to release the secondary shifter when the actuating shaft is rotated in the direction to sepa-rate the electrodes, mechanism for return- Cil 20 ing the secondary shifter at a controlled rate of movement, and a tail piece on said latch member engageable with a portion of secondary shifter to prevent rotation of the actuating shaft and separation of the electrodes until the secondary shifter has returned to a position to establish wear compensating connection between the primary shifter and the movable electrodes.

GODFREY P. GOODE.

CARL K. GIERINGER.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS 

